Halftone is the reprographic technique that simulates continuous-tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect. "Halftone" can also be used to refer specifically to the image that is produced by this process.
William Henry Fox Talbot FRS FRSE FRAS was an English scientist, inventor, and photography pioneer who invented the salted paper and calotype processes, precursors to photographic processes of the later 19th and 20th centuries. His work in the 1840s on photomechanical reproduction led to the creation of the photoglyphic engraving process, the precursor to photogravure. He was the holder of a controversial patent that affected the early development of commercial photography in Britain. He was also a noted photographer who contributed to the development of photography as an artistic medium. He published The Pencil of Nature (1844–1846), which was illustrated with original salted paper prints from his calotype negatives and made some important early photographs of Oxford, Paris, Reading, and York.
Photographic paper is a paper coated with a light-sensitive chemical formula, like photographic film, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image that is then developed to form a visible image; with most papers the image density from exposure can be sufficient to not require further development, aside from fixing and clearing, though latent exposure is also usually present. The light-sensitive layer of the paper is called the emulsion. The most common chemistry was based on silver halide but other alternatives have also been used.
Frederic Eugene Ives was a U.S. inventor who was born in Litchfield, Connecticut. In 1874–78 he had charge of the photographic laboratory at Cornell University. He moved to Philadelphia, Pennsylvania, where in 1885 he was one of the founding members of the Photographic Society of Philadelphia. He was awarded the Franklin Institute's Elliott Cresson Medal in 1893, the Edward Longstreth Medal in 1903, and the John Scott Medal in 1887, 1890, 1904 and 1906. His son Herbert E. Ives was a pioneer of television and telephotography, including color facsimile.
Photogravure is a process for printing photographs, also sometimes used for reproductive intaglio printmaking. It is a photo-mechanical process whereby a copper plate is grained and then coated with a light-sensitive gelatin tissue which had been exposed to a film positive, and then etched, resulting in a high quality intaglio plate that can reproduce detailed continuous tones of a photograph.
Platinum prints, also called platinotypes, are photographic prints made by a monochrome printing process involving platinum.
Color printing or colour printing is the reproduction of an image or text in color. Any natural scene or color photograph can be optically and physiologically dissected into three primary colors, red, green and blue, roughly equal amounts of which give rise to the perception of white, and different proportions of which give rise to the visual sensations of all other colors. The additive combination of any two primary colors in roughly equal proportion gives rise to the perception of a secondary color. For example, red and green yields yellow, red and blue yields magenta, and green and blue yield cyan. Only yellow is counter-intuitive. Yellow, cyan and magenta are merely the "basic" secondary colors: unequal mixtures of the primaries give rise to perception of many other colors all of which may be considered "tertiary".
Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health. It is a crystalline ionic solid with a very bright, red-orange color. The salt is popular in laboratories because it is not deliquescent, in contrast to the more industrially relevant salt sodium dichromate.
Photoengraving is a process that uses a light-sensitive photoresist applied to the surface to be engraved to create a mask that protects some areas during a subsequent operation which etches, dissolves, or otherwise removes some or all of the material from the unshielded areas of a substrate. Normally applied to metal, it can also be used on glass, plastic and other materials.
The term alternative process refers to any non-traditional or non-commercial photographic printing process. Currently the standard analog photographic printing process is the gelatin silver process, and standard digital processes include the pigment print, and digital laser exposures on traditional color photographic paper.
A carbon print is a photographic print with an image consisting of pigmented gelatin, rather than of silver or other metallic particles suspended in a uniform layer of gelatin, as in typical black-and-white prints, or of chromogenic dyes, as in typical photographic color prints.
Gum bichromate is a 19th-century photographic printing process based on the light sensitivity of dichromates. It is capable of rendering painterly images from photographic negatives. Gum printing is traditionally a multi-layered printing process, but satisfactory results may be obtained from a single pass. Any color can be used for gum printing, so natural-color photographs are also possible by using this technique in layers.
Collotype is a gelatin-based photographic printing process invented by Alphonse Poitevin in 1855 to print images in a wide variety of tones without the need for halftone screens. The majority of collotypes were produced between the 1870s and 1920s. It was the first form of photolithography.
The following outline is provided as an overview of and topical guide to photography:
Walter Bentley Woodbury was an inventor and pioneering English photographer. He was an early photographer in Australia and the Dutch East Indies. He also patented numerous inventions relating to various aspects of photography, his best-known innovation being the woodburytype photomechanical process.
Screenless lithography is a reprographic technique for halftoning dating to 1855, when the French chemist and civil engineer Alphonse Poitevin discovered the light–sensitive properties of bichromated gelatin and invented both the photolithography and collotype processes. After the invention of the halftone screen in the 1880s, screenless lithography was abandoned. Until the end of World War II, two kinds of photomechanically made plates were used in lithography: albumin plates and deep-etch plates. Presensitized plates appeared in the 1950s, and wipe–on plates appeared in the 1960s.
The David A. Hanson Collection of the History of Photomechanical Reproduction is a collection at the Clark Art Institute Library documenting the history of the development of photography from 1826 to the early 20th century. It includes all kinds of photography as well as books and articles. It was assembled by David A. Hanson.
The oil print process is a photographic printmaking process that dates to the mid-19th century. Oil prints are made on paper on which a thick gelatin layer has been sensitized to light using dichromate salts. After the paper is exposed to light through a negative, the gelatin emulsion is treated in such a way that highly exposed areas take up an oil-based paint, forming the photographic image.
